#include <stdio.h>
int Fib(int n) {
    int a = 1;
    int b = 1;
    int c = 1;
    while (n>2) {
        c = a+b;
        a = b;
        b = c;
        n--;
    }
    return c;
}
int main() {
    int n = 0;
    scanf("%d", &n);
    printf("%d\n", Fib(n));
    return 0;
}